Researchers: Chemical attracts sperm to egg

Posted: Monday, March 31, 2003

By Paul RecerAssociated Press

WASHINGTON - A new study proves that human male sperm will swim toward chemical attractants to find the female egg, a discovery researchers say could lead to new ways to treat infertility or to new contraceptives that do not use hormones.

In a study appearing Friday in the journal Science, researchers report they have found that human sperm has a receptor, or chemical sensor, that causes the sperm to swim vigorously toward concentrations of a chemical attractant.

The new study used a laboratory compound called bourgeonal to prove that sperm are attracted by chemical signals, said Richard K. Zimmer, a professor of biology at the University of California, Los Angeles, who co-authored the study.

A precise compound in the human female reproductive tract that works like bourgeonal has not been found, but it is widely believed among experts that such a chemical exists.

Zimmer said the researchers also identified another compound, called undecanal, that shuts down the sperm chemical sensor and keeps it from responding to an attractant.

Although much more research must be done, Zimmer said the twin discoveries could lead to new drugs that could, depending on their use, overcome some fertility problems or inhibit conception.

Some human reproduction researchers said the study by Zimmer and his co-authors is a significant advance in understanding how the sperm and egg find each other.

"This is a landmark piece of work," said Dr. Donner F. Babcock, a researcher at the University of Washington in Seattle. "The holy grail in reproductive biology has been to find the sperm attractant and to understand how it works.

"This is the strongest evidence we have so far that the egg signals its location to the sperm and the sperm responds by swimming toward the egg," said Babcock.

In the study, Zimmer and his co-authors at UCLA and the Ruhr University Bochum in Germany demonstrate that the surface of human sperm has a receptor, called hOR17-4, that causes the sperm to navigate in a specific direction when it detects a concentration of bourgeonal.

It long has been known that there are chemical signals between the female egg and the male sperm that help the two to find each other. But the new study is the first to demonstrate that the sperm will respond in a predicable and controllable way to a chemical signal.